1. Field of the Invention
The invention concerns apparatus and methods of culturing microorganisms and more particularly concerns an assembly and the method of its use to protect anaerobes from exposure to gaseous oxygen during the period between isolation from a clinical patient and inoculation into an environment conductive to culturing.
2. Brief Description of the Prior Art
In recent years there has been an increased awareness of the importance of diagnosing anaerobic infections. Apparatus and techniques for culturing and differentiating anaerobes have been developed and refined for diagnosing and differentiating anerobic infections and the causative organisms; see for example the apparatus disclosed in U.S. Pat. No. 3,246,959.
However, the weak link in the overall procedure of collecting a clinical specimen, carrying the specimen to the laboratory and culturing the organisms therein has been in the transportation step. If in transporting the specimen from the clinical patient to the laboratory, the specimen is exposed to gaseous oxygen, the oxygen sensitive anaerobes are eliminated and the subsequent differentiation is inaccurate. Many strains of anaerobes are highly sensitive to oxygen and will not survive even brief exposures to gaseous oxygen.
A review of the prior art methods and apparatus for transporting anaerobes between clinical source and laboratory may be found in the Scope monograph on Anaerobic Infections published by The Upjohn Company, Kalamazoo, Michigan (1972) at pages 54-55 (Library of Congress Card No. 72-79754). In brief, these methods have comprised either rapidly placing a swab collection or specimen in a carbon dioxide filled container, a transport medium, or drawing a liquid specimen into a syringe and then injecting the specimen into an anaerobe bottle. Of these methods, the latter is most likely to maintain strict anaerobiosis provided the specimen is not aspirated with air during collection. The employment of reduced transport medium for anaerobes has not been encouraging; see for example Yrios et al., Abstracts of the Annual Meeting of the ASM, (1974). The Scope monograph reference describes transporting anaerobe suspect organisms on cotton swabs protected from exposure to oxygen by immersion in a pre-reduced, anaerobically sterilized Cary-Blair medium in either a tube or a vial with a mineral oil overlay.
A transporter device is described in U.S. Pat. No. 3,773,035 which is specifically useful in transporting and culturing gonorrhea under a carbon dioxide atmosphere. Other devices representative of the prior art are disclosed in U.S. Pat. Nos. 3,483,089 and 3,750,646.
The method and assembly of the invention incorporates the concept of placing the clinical specimen into an anaerobic environment as rapidly as possible. The methods and apparatus of the prior art all include some time lag in accomplishing this objective. Further, unlike simply placing the clinical specimen into a carbon dioxide filled tube, the amount of air entering the assembly of the invention is limited. The maximum amount of gaseous oxygen to which the specimen is exposed within the assembly of the invention is about 2 percent by volume. This small amount is then rapidly removed as will be hereinafter described.
The apparatus and method of the invention are relatively simple in comparison to the prior art apparatus and methods. The apparatus is constructed readily at low cost and requires a minimum amount of training for operation. In addition, the method of the invention has shown great reliability in operation and assures transportation of viable microbes even for prolonged periods. The assembly of the invention permits one to obtain minimal exposure of a specimen to oxygen.